Battery and preparation method thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a battery and a preparation method thereof.The method comprises the steps that after a battery cell and a shell are packaged, primary liquid injection and fixture formation are conducted through electrolyte A, and a semi-finished product battery is obtained; the electrolyte A in the semi-finished battery is extracted, and the extraction weight ratio is 10%-90%; and carrying out secondary liquid injection on the semi-finished battery by using the electrolyte B, and sealing and packaging to obtain the battery, wherein the composition of the electrolyte A is different from that of the electrolyte B, and the weight ratio of the secondary injection liquid and the extraction weight ratio can be different or the same and are determined according to product performance requirements. By improving the liquid injection mode of the battery, formation is carried out after first liquid injection, then the electrolyte participating in the reaction is extracted, and the same amount of new electrolyte with different performances is injected again, so that the injected new electrolyte can remarkably prolong the cycle life of the lithium battery or improve various safety performances of the battery; the performance of thermal shock, overcharge, heavy object impact, needling and the like can be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a battery and a preparation method thereof. Background Art

[0002] The existing lithium battery injection adopts primary injection (consumer soft pack battery) or secondary injection (energy storage, power aluminum shell battery). Regardless of primary or secondary injection, the injected electrolyte is the same type of electrolyte, so that the lithium battery forms a better SEI and CEI film during formation, and continuously repairs the damaged SEI and CEI film during the subsequent cycle process, thus ensuring the cycle life of the battery.

[0003] However, when these two types of batteries are formed, the electrolyte will react with the positive and negative electrodes of the lithium battery, impurities, etc. to form SEI, CEI membranes or other side reaction products, resulting in partial changes in the composition of the electrolyte. The original electrolyte additives contribute greatly to the formation, but after the formation, some components in the electrolyte are no longer suitable for the requirements of lithium battery cycles. Summary of the invention

[0004] The purpose of the present invention is to provide a battery and a method for preparing the same in order to improve the liquid injection method in the battery preparation process and thus increase the cycle life and safety performance of the battery.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a battery comprises the following steps:

[0007] Step (1): After the battery cell and the shell are packaged, electrolyte A is injected once and the fixture is formed to obtain a semi-finished battery;

[0008] Step (2): extracting the electrolyte A formed in the semi-finished battery of step (1), with the weight ratio of the electrolyte A being 10% to 90%;

[0009] Step (3): injecting electrolyte B into the semi-finished battery after the electrolyte A is extracted in step (2) for the second time, with the extraction weight ratio being 10%-90%, and sealing and packaging to obtain the battery;

[0010] Among them, the compositions of the electrolyte A in step (1) and the electrolyte B in step (3) are different; the weight ratio of the secondary injection in step (3) is similar to the weight ratio of the extraction in step (2).

[0011] In the preparation method provided by the present invention, the electrolyte A and the electrolyte B have different formula compositions, wherein the electrolyte A can appropriately add a first additive for forming a more stable SEI film, and the electrolyte B can add different second additives, such as high cycle performance additives, heat shock resistance additives, overcharge protection additives, flame retardant additives, etc., according to the performance differences of the battery material system or the actual use of the battery. After adding a sufficient amount of electrolyte A, it can be ensured that the battery core is completely infiltrated by the electrolyte, and the negative electrode can form a dense SEI film during formation. After the formation is completed, the consumed electrolyte A is extracted and then re-injected with a new electrolyte B. The electrolyte B contains a second additive suitable for different production needs and optimizes and improves battery performance. The extraction weight ratio is similar to the secondary injection weight ratio, and can be the same or different weight ratio, depending on the product performance requirements, so as to supplement enough free electrolyte to meet the consumption of electrolyte during battery use.

[0012] Preferably, the electrolyte A in step (1) comprises a solvent, a lithium salt and a first additive;

[0013] The solvent includes any one of EC, EMC, PC, and DEC or a combination of at least two thereof;

[0014] The lithium salt includes LiPF 6 、LiClO 4 , any one of LiBOB, LiFSI, LiODFB, LiTFSI or a combination of at least two;

[0015] The first additive includes any one of FEC, PS, and ADA, or a combination of at least two of them.

[0016] The electrolyte A can effectively form a SEI film during formation, and various components in the electrolyte A will also be consumed.

[0017] Preferably, the electrolyte B in step (3) comprises a solvent, a lithium salt and a second additive;

[0018] The solvent includes any one of EC, EMC, PC, DEC or a combination of at least two thereof.

[0019] The lithium salt includes LiPF 6 、LiClO 4 , any one of LiBOB, LiFSI, LiODFB, LiTFSI or a combination of at least two;

[0020] The second additive includes any one of a high cycle performance additive, an anti-thermal shock additive, an overcharge protection additive, and a flame retardant additive, or a combination of at least two thereof.

[0021] The electrolyte B is re-injected after the electrolyte A is extracted, and it does not participate in the formation of the film, which can effectively reduce the impedance of the battery and reduce the polarization of the battery. At the same time, it meets the performance improvement of various aspects of the battery for different production needs.

[0022] Preferably, the high cycle performance additives include VC, SO 2 , FEC, HTCN, LiODFB, or any one thereof, or a combination of at least two thereof. The use of the above additives can effectively improve the battery cycle performance.

[0023] Preferably, the thermal shock resistance additive includes any one of phosphoric acid cyclic anhydride compounds, sultone compounds, and nitrile compounds, or a combination of at least two of them. The use of the above additives can effectively improve the thermal shock resistance of the battery.

[0024] Preferably, the overcharge protection additive includes any one of cyclobenzene, dihexylbenzene, and a redox couple additive, or a combination of at least two of them. The use of the above additives can effectively improve the safety performance of the battery under overcharge conditions.

[0025] Preferably, the flame retardant additive includes any one of an organic phosphorus flame retardant additive, a nitrogen compound flame retardant additive, a halogenated carbonate flame retardant additive, and a silicon flame retardant additive, or a combination of at least two of them. The use of the above additives can effectively improve the safety performance of the battery when it encounters heavy impact or sharp puncture.

[0026] Preferably, the electrolyte A is extracted in step (2) by centrifugal or high-pressure extrusion. The purpose is to extract the electrolyte A as much as possible to introduce the new performance-enhancing additive B.

[0027] Preferably, the weight proportion of the extracted electrolyte A and the weight proportion of the secondary injection of the electrolyte B are both 80%-90%.

[0028] A battery is prepared by any one of the above-mentioned battery preparation methods.

[0029] Compared with the prior art, the beneficial effect of the present invention is that: the battery and its preparation method provided by the present invention improve the battery injection method, perform formation after the first injection, then extract the electrolyte that has participated in the reaction, and then re-inject an equal amount of new electrolyte with different properties. The original electrolyte consumes its own effective components to form an SEI film during the formation process, which leads to a certain decrease in cycle performance during the subsequent use of the battery. By injecting a new electrolyte, sufficient free electrolyte can be provided to meet the consumption of the electrolyte during the use of the battery. And the injected new electrolyte can significantly improve the cycle life of the lithium battery or improve various safety properties of the battery, such as thermal shock, overcharge, heavy object impact, acupuncture and other properties. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1:

[0032] This example prepares the battery according to the following method:

[0033] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0034] (2) Prepare electrolyte B1: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a second additive is added and mixed evenly to obtain an electrolyte B1, wherein the solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the mass ratio of EC to EMC in the solvent is EC:EMC=3:7, and the second additive is vinylene carbonate (VC) and fluoroethylene carbonate (FEC), and the mass ratio of the second additive VC to FEC is VC:FEC=8:3.

[0035] (3) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; placing the semi-finished battery on a centrifugal disk to centrifuge the electrolyte A therein, the extracted weight ratio being 85%, and then re-injecting an equal amount of electrolyte B1, and sealing and packaging to obtain the battery.

[0036] Embodiment 2:

[0037] The battery preparation method provided in this embodiment is the same as that of Embodiment 1 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 55%.

[0038] Embodiment 3:

[0039] The battery preparation method provided in this embodiment is the same as that of Embodiment 1 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 15%.

[0040] Embodiment 4:

[0041] This example prepares the battery according to the following method:

[0042] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0043] (2) Prepare electrolyte B2: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a second additive is added and mixed evenly to obtain an electrolyte B2, wherein the solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the mass ratio of EC to EMC in the solvent is EC:EMC=3:7, and the second additive is a nitrile compound.

[0044] (3) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; placing the semi-finished battery on a centrifugal disk to centrifuge the electrolyte A therein, the extracted weight ratio being 85%, and then re-injecting an equal amount of electrolyte B2, and sealing and packaging to obtain the battery.

[0045] Embodiment 5:

[0046] The battery preparation method provided in this embodiment is the same as that of embodiment 4 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 55%.

[0047] Embodiment 6:

[0048] The battery preparation method provided in this embodiment is the same as that of embodiment 4 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 15%.

[0049] Embodiment 7:

[0050] This example prepares the battery according to the following method:

[0051] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0052] (2) Prepare electrolyte B3: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a second additive is added and mixed evenly to obtain an electrolyte B3, wherein the solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the mass ratio of EC to EMC in the solvent is EC:EMC=3:7, and the second additive is cyclobenzene.

[0053] (3) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; placing the semi-finished battery on a centrifugal disk to centrifuge the electrolyte A therein, the extracted weight ratio being 85%, and then re-injecting an equal amount of electrolyte B3, and sealing and packaging to obtain the battery.

[0054] Embodiment 8:

[0055] The battery preparation method provided in this embodiment is the same as that of Embodiment 7 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 55%.

[0056] Embodiment 9:

[0057] The battery preparation method provided in this embodiment is the same as that of Embodiment 7 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 15%.

[0058] Embodiment 10:

[0059] This example prepares the battery according to the following method:

[0060] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0061] (2) Prepare electrolyte B4: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a second additive is added and mixed evenly to obtain an electrolyte B4, wherein the solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the mass ratio of EC to EMC in the solvent is EC:EMC=3:7, and the second additive is a silicon-based flame retardant additive.

[0062] (3) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; placing the semi-finished battery on a centrifugal disk to centrifuge the electrolyte A therein, the extracted weight ratio being 85%, and then re-injecting an equal amount of electrolyte B4, and sealing and packaging to obtain the battery.

[0063] Embodiment 11:

[0064] The battery preparation method provided in this embodiment is the same as that of Embodiment 10 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 55%.

[0065] Embodiment 12:

[0066] The battery preparation method provided in this embodiment is the same as that of Embodiment 10 except that the weight ratio of electrolyte A extracted in step (3) during battery preparation is 15%.

[0067] Comparative Example 1:

[0068] This example prepares the battery according to the following method:

[0069] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0070] (2) Making a battery: placing the battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it at room temperature for 24 hours, and then performing clamp formation to prepare a battery. Comparative Example 2:

[0071] This example prepares the battery according to the following method:

[0072] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0073] (2) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting electrolyte A having a weight ratio of 80% of that in comparative example 1 into the aluminum-plastic film, leaving the film to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; after formation, injecting electrolyte A having a weight ratio of 20% of that in comparative example 1 again, and sealing and packaging to obtain the battery.

[0074] Comparative Example 3:

[0075] This example prepares the battery according to the following method:

[0076] (1) Prepare electrolyte A: Lithium perchlorate (LiClO 4 ) is added to a solvent, and a first additive is added and mixed evenly to obtain an electrolyte A, wherein the solvent is a mixture of ethylene carbonate (EC), propylene carbonate (PC) and ethyl methyl carbonate (EMC), and the mass ratio of EC, PC and EMC in the solvent is EC:PC:EMC=30:5:65, and the first additive is fluoroethylene carbonate (FEC) and propylene sulfite (PS), and the mass ratio of the first additive FEC and PS is FEC:PS=3:2.

[0077] (2) Making a battery: placing a battery cell in an aluminum-plastic film and performing preliminary packaging, then injecting a sufficient amount of electrolyte A into the aluminum-plastic film, leaving it to stand at room temperature for 24 hours, and then performing clamp formation to obtain a semi-finished battery; placing the semi-finished battery on a centrifugal disk to centrifuge and extract the electrolyte A therein, with the extracted weight ratio being 85%, and then re-injecting an equal amount of electrolyte A, and sealing and packaging to obtain the battery.

[0078] The batteries prepared in the above embodiments and comparative examples were subjected to various performance tests, and the specific test results are shown in Table 1.

[0079] Table 1

[0080]

[0081] It can be seen from the combined examples and comparative examples that, by adopting the method of injecting electrolyte A once and injecting electrolyte B twice, the first additive injected into electrolyte A once can effectively form a SEI film during formation; and the second additive in electrolyte B is injected twice, which can ensure the performance of the battery in actual use. At the same time, electrolyte B does not participate in the formation and film formation, which can effectively reduce the impedance of the battery and reduce the polarization of the battery.

[0082] It can be seen from Examples 1-3 that, during the secondary injection, the greater the weight proportion of electrolyte B re-injected, the more cycles the battery can undergo, and the better the overall cycle performance of the battery.

[0083] It can be seen from Example 1 and Comparative Examples 1-3 that the battery cycle number gradually increases and the overall cycle performance of the battery is enhanced from directly forming with a sufficient amount of electrolyte A, to forming with part of the electrolyte and then supplementing the remaining part, and after the electrolyte A is extracted and replaced after the first injection. When the same electrolyte A is replaced, the cycle performance is enhanced but not obvious, and when another electrolyte B is replaced, the cycle performance is significantly improved.

[0084] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a battery, characterized in that: The steps include: Step (1): After the battery cell and the shell are packaged, electrolyte A is injected once and the fixture is formed to obtain a semi-finished battery; Step (2): extracting the electrolyte A formed in the semi-finished battery of step (1), with the weight ratio of the electrolyte A being 10% to 90%; Step (3): injecting electrolyte B into the semi-finished battery after the electrolyte A is extracted in step (2) for the second time, extracting electrolyte B in a weight ratio of 10% to 90%, and sealing and packaging to obtain the battery; Among them, the compositions of the electrolyte A in step (1) and the electrolyte B in step (3) are different; the weight ratio of the secondary injection in step (3) is similar to the weight ratio of the extraction in step (2).

2. The method for preparing a battery according to claim 1, characterized in that: The electrolyte A in step (1) comprises a solvent, a lithium salt and a first additive; The solvent includes any one of EC, EMC, PC, DEC or a combination of at least two thereof. The lithium salt includes any one or a combination of at least two of LiPF6, LiClO4, LiBOB, LiFSI, LiODFB, and LiTFSI; The first additive includes any one of FEC, PS, and ADA, or a combination of at least two of them.

3. The method for preparing a battery according to claim 2, characterized in that: The electrolyte B in step (3) comprises a solvent, a lithium salt and a second additive; The solvent includes any one of EC, EMC, PC, DEC or a combination of at least two thereof. The lithium salt includes any one or a combination of at least two of LiPF6, LiClO4, LiBOB, LiFSI, LiODFB, and LiTFSI; The second additive includes any one of a high cycle performance additive, an anti-thermal shock additive, an overcharge protection additive, and a flame retardant additive, or a combination of at least two thereof.

4. The method for preparing a battery according to claim 3, characterized in that: The high cycle performance additive includes any one of VC, SO2, FEC, HTCN, and LiODFB, or a combination of at least two of them.

5. The method for preparing a battery according to claim 3, characterized in that: The heat shock resistant additive includes any one of phosphoric acid cyclic anhydride compounds, sultone compounds, and nitrile compounds, or a combination of at least two of them.

6. The method for preparing a battery according to claim 3, characterized in that: The overcharge protection additive includes any one of cyclobenzene, dihexylbenzene, and redox couple additives, or a combination of at least two of them.

7. The method for preparing a battery according to claim 3, characterized in that: The flame retardant additive includes any one of an organic phosphorus flame retardant additive, a nitrogen-containing compound flame retardant additive, a halogenated carbonate flame retardant additive, and a silicon flame retardant additive, or a combination of at least two thereof.

8. The method for preparing a battery according to claim 1, characterized in that: The electrolyte A in step (2) is extracted by centrifugal extraction or high-pressure extrusion.

9. The method for preparing a battery according to claim 1, characterized in that: The weight proportion of the extracted electrolyte A and the weight proportion of the secondary injection of the electrolyte B are both 80%-90%.

10. A battery, characterized in that: The battery is prepared by the method for preparing a battery as described in any one of claims 1 to 9.

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